1. Field of the Invention
The present invention is directed to a medical apparatus of the type having a carrying device for at least one component, the carrying device being adjustable relative to a holding mechanism.
2. Description of the Prior Art
German PS 42 14 858, corresponding to U.S. Pat. No. 5,425,068, discloses a medical apparatus of the type initially described. The medical apparatus is an X-ray device with carrying device in the form of a C-arm carrying an X-ray source and an X-ray image intensifier, this carrying device being mounted so as to be adjustable along its circumference in a holding mechanism. The C-arm is formed of plastic and has two guide rails of metal at both sides in the region of the greatest expanse of its cross-section, rollers for the adjustment of the C-arm relative to the holding mechanism running on these rails. The guide rails of metal are required in order to keep the rolling friction drag and the wear low. The presence of the guide rails is also required in order to absorb the forces acting on the C-arm due to the rollers of the holding mechanism.
Such a C-arm is usually weight-compensated in order to enable manual adjustment of the C-arm relative to the holding mechanism. The X-ray source, the X-ray image intensifier and the C-arm are thereby balanced relative to the pivot point of the C-arm by appropriate attachment of compensation weights to, for example, the C-arm. A disadvantage of this known C-arm is that the beam path of the central ray of an X-ray beam emanating from the X-ray source does not proceed through the pivot point of the C-arm, i.e. the C-arm does not have an isocenter. In a radiological examination of a subject with the assistance of the known C-arm X-ray device wherein the subject is positioned in the beam path of the central ray of an X-ray beam emanating from the X-ray source, the subject, given a change of the projection direction due to adjustment of the C-arm along its circumference relative to the subject, is then only partially in the beam path of the central ray of the X-ray beam or not at all, causing the X-ray image of the subject under examination, that is usually displayed on the picture screen of a viewing means, to migrate across the picture screen or to be entirely out of the picture screen. The migration of the subject across or out of the picture screen therefore requires a repositioning of the C-arm relative to the subject, causing the medical examination to be lengthened and causing the patient to be subjected to an additional radiation exposure.
U.S. Pat. No. Re. 34,943 discloses an X-ray device with a C-arm formed of an aluminum alloy that carries an X-ray source, an adjustable X-ray image intensifier and an adjustable balancing weight, wherein the beam path of the central ray of an X-ray beam emanating from the X-ray source proceeds through the pivot point of the C-arm. A disadvantage is that this X-ray device is not suitable for mobile use since it would fall over forwards due to the weight of the X-ray source, the X-ray image intensifier, the balancing weight and the dead weight of the C-arm, all of which would have to be arranged at an apparatus cart of the X-ray device if it were to be made mobile. Counterweights that could compensate for the heavy metal arc, the X-ray source, the X-ray image intensifier and the balancing weight could not be employed for weight reasons, since the mobility and the positionability of the X-ray device would be substantially restricted due to the heavy weight which would be required.
Even given an embodiment of the C-arm according to German PS 42 14 858, the X-ray device would still exhibit such a high dead weight that it would not be suitable for mobile use.
Although German PS 40 03 350 discloses a mobile C-arm X-ray device whose C-arm seated in a holding mechanism comprises an isocenter, the C-arm is not provided with balancing weights such that the C-bend could be unproblematically manually adjusted in the holding mechanism.